Laser energy attenuation paint

ABSTRACT

The present invention relates to a laser energy attenuation paint  compris a laser absorption dye in combination with a resin base in a solvent.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a paint formulation which is effectivein attenuating laser energy.

2. Description of the Prior Art

In the past laser beams have been used to cure paint coatings, among themany other uses for laser beams. In particular it has been found thatthe infrared radiation from a laser is effective in promoting the curingof paint coatings.

Attempts have been made in the past to attenuate laser energy in safetyrelated applications. These applications have used solid plastic sheetsof material impregnated with a laser absorption dye. However, solidplastic material has not proved to be satisfactory in many laserattenuation applications. The problems involved with the use of solidlaser attenuation materials have included the inability of the solidmaterial to adhere to surfaces other than flat surfaces, difficulties inapplication to large areas, and the fact that attenuation is onlyprovided in large quantum steps. An example is an optical density of 16or 160 db of attenuation. A need therefore continues to exist for alaser attentuation technique which overcomes the above describeddifficulties.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide a laserattenuation medium which is not encumbered with the problems of past andcontemporary laser attenuation media, in that it is capable of beingapplied over large surface areas and on objects of widely varying shapesand sizes.

Briefly, this object and other objects of the present invention ashereinafter will become more readily apparent can be attained by a laserattenuation paint which is a laser attenuation dye in combination with aresin base in a solvent.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The discovery of the present invention is a laser energy attenuationpaint (LEAP) which, when applied to a surface, dries into a hard thinfilm. The thickness of an applied layer of the present laser attenuationpaint is a function of the extent of attenuation desired with the extentof attenuation being directly proportional to the thickness of theapplied layer. Accordingly, any desired attenuation can be obtained byapplying succeeding layers of laser attenuation paint to an object.Moreover, the laser attenuation paint can be so formulated that althoughlaser energy is attenuated or absorbed, the paint is transparent to thevisible region of the spectrum.

The LEAP formulation of the present invention can be easily applied tosurfaces of any shape, and, in fact, can be combined with granularsubstances such as dust, sand, salt and the like to simultaneouslyachieve attenuation and diffusion by absorption of laser light.

The laser attenuation paint of the present invention is based on thediscovery that the laser absorption dye used in laser guard materialscan be dissolved in a solvent base, and when applied to a substrate,will effectively attenuate laser light. The essential criterion for theselection of a dye for use in the paint is that it must be compatiblewith the light from a specific laser. In other words, since the lightfrom a given laser is of one particular wavelength, the absorption dyeused must be of the color which is capable of attenuating thatparticular wavelength of laser light. Thus, in order to attenuate thelight from a helium-neon or ruby laser, the dye of the paint must be ablue dye. For neodymium Yag and gallium arsenide lasers, a dark greendye must be used. For argon lasers, an orange/red dye must be used; andfor a CO₂ laser, a clear paint may be employed. Other types of laserswould require a dye falling within these four basic colors.

The type of dye molecule which is used is not an important or criticalconsideration. Of course, it must be dissolvable in the solvent of thepaint formulation. However, the dyes themselves are not limited to anyparticular one or several types of dye classes. The dye selected mustonly be of a color which is appropriate to absorb the light from a givenlaser.

In order to prepare the laser attenuation paint, the laser absorptiondye, along with a resin, is dissolved in a solvent. The resin which isselected may be any type of thermoplastic material, with acrylic resinsbeing the preferred resins. The resin, of course, should facilitate thelaser light attenuation effect and certainly not detract from it.

The solvent which is employed to complete the paint formulation mustdissolve the dye and resin components, and should be a relatively lowboiling point material so as to evaporate from the applied paint.Suitable solvents include aliphatic ketones such as acetone,methylethylketone, or the like; halogenated hydrocarbons such asmethylene chloride, chloroform, ethylene dichloride, and the like;esters such as methyl acetate, ethyl acetate, methyl propionate, and thelike; and aromatic hydrocarbon compounds such as benzene, toluene, andthe like. Combinations of these solvents may be employed, and, in fact,a preferred solvent system is a combination of acetone and methylenechloride.

The amounts of resin and laser dye which are incorporated in a paintformulation are not critical. The amount of dye incorporated in thepaint should be such an amount that when a layer of paint is applied toa surface, an attenuation of laser light to an extent of one to several,preferably about 3 db is obtained. The amount of resin incorporated inthe paint should be an amount sufficient to fix the laser dye on thepainted surface, and to provide a sufficient coating of resin when alayer of paint is applied to a surface. Normally, the amount of laserabsorption dye in the paint ranges from about 1% up to about 20%, andthe amount of resin component may range from about 5% to 50%. Thesolvent, of course, comprises the remainder of the paint formulation.

If desired, the laser absorption paint can contain other paint additivessuch as carbon black, barium sulfate, calcium sulfate or the like. Thefour materials, when present, are used in customary amounts for paintformulations.

Once the laser attenuation paint of the invention is applied to asubstrate, the paint dries rapidly, thereby leaving an effective laserlight attenuating coating.

The laser attenuation paint of the present invention can be easilyapplied to many different types and shapes of substrates. LEAPinexpensively converts common transparent substances such as glass intoattenuation filters or eye safety shields. Of more importance is thefact that curved surfaces such as lenses can be made to attenuate laserradiation. Another feature of LEAP is that it can be combined withgranular or crystalline substances such that when it is applied tosurfaces, it simultaneously affects attenuation, absorption anddiffusion of light which greatly reduces the light reflected from atarget. The present laser attenuation paint can conceivably be paintedon a target to decrease the reflectance from a target designator whichuses laser energy, thereby decreasing the range of a laser guidedweapon.

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples which are providedherein for purposes of illustration only and are not intended to belimiting unless otherwise specified.

A laser attenuation paint was prepared by dissolving 2 g of acrylicplastic sheet material, which contained green pigment, in a solvent of 6fl. oz. of methylene chloride, acetone or ethylene dichloride. Sixsquare pieces of glass were each coated with a different number of paintcoatings so that the number of coatings on the glass pieces ranged fromone to six. As the solvent evaporated after each coating, a thin film ofpigment in resin remained. A separate glass piece was prepared which hadno coating of LEAP. Using a 0.25 watt CW Yag GTE Sylvania model 605laser and a EGG 580 radiometer, attenuated laser light was measuredthrough each glass piece, and the following values were obtained. Eachcoating of paint provided about 3 db of attenuation.

    ______________________________________                                        Number of LEAP                                                                Coatings on Glass Piece                                                                        Radiometer Value                                             ______________________________________                                        0 (clear)         8 × 10.sup.-9                                         one              3.7 × 10.sup.-9                                        two              2.1 × 10.sup.-9                                        three            0.5 × 10.sup.-10                                       four             2.0 × 10.sup.-10                                       five             1.0 × 10.sup.-10                                       six              0.5 × 10.sup.-10                                       ______________________________________                                    

Having now fully described the invention, it will be apparent to one ofordinary skill in the art that many changes and modifications can bemade thereto without departing from the spirit or scope of the inventionas set forth herein.

What is claimed as new and is intended to be secured by Letters Patentis:
 1. A laser energy attenuation paint, comprising:a laser absorptiondye in combination with a resin base in a solvent.
 2. The laser energyattenuation paint of claim 1, wherein said solvent is an aliphaticketone, a halogenated hydrocarbon, an ester, an aromatic hydrocarbon ormixtures thereof.
 3. The laser energy attenuation paint of claim 2,wherein said solvent is acetone, methylene chloride and/or ethylenedichloride.
 4. The laser energy attenuation paint of claim 3, whereinsaid solvent is a combination of acetone and methylene chloride.
 5. Thelaser energy attenuation paint of claim 1, wherein said laser absorptiondye is a dark blue dye, a dark green dye, a red dye or an orange dye, orcombination thereof.
 6. The laser energy absorption paint of claim 1,wherein the laser absorption dye is a dark blue dye which absorbs lightfrom a helium-neon or ruby laser.
 7. The laser energy absorption paintof claim 1, wherein the laser absorption dye is a dark green dye forgallium arsenide and neodymium Yag lasers.
 8. The laser energyabsorption paint of claim 1, wherein the laser absorption dye is anorange/red dye for argon lasers.
 9. The laser energy absorption paint ofclaim 1, wherein said resin is a thermoplastic resin.
 10. The laserenergy absorption paint of claim 9, wherein said resin is a clearacrylic resin.